For those of you who installed the Windows Phone 8 GDR3 Preview update, there is an update available for you right now. This bumps the operating system build number to 8.0.10521.155.

Microsoft recently launched the Preview Program for its developers, which allows you to snag the GDR3 update – as well as future updates – immediately if you have a registered developer account. This new update today is available for those who are on this Preview Program.

The updates available are: Microsoft Update 8.0.10517.150 and Microsoft Update 8.0.10521.155. These are updates from Microsoft for the Windows Phone operating system and are not firmware updates from Nokia.

We’ve installed these updates and have noticed no visible changes in Windows Phone 8. Perhaps this was just an update to GDR3 (aka Update 3) fixing bugs along the way or perhaps this update brought us the final build of GDR3.

We asked Microsoft for a change log and were told that no change log was available. However, a Microsoft spokesperson told WinBeta today that these two updates are simply minor bug fixes.

Let us know if you were able to successfully update and if you noticed any new improvements.